The present invention relates to the diagnostic imaging arts. It finds particular application in conjunction with an integrated angiographic and computerized tomographic (CT) diagnostic imaging system and will be described with particular reference thereto. However, it should be appreciated that the present invention may also find application in conjunction with other types of multi-modality diagnostic imaging systems.
Conventional x-ray angiography is an examination where a contrast material that is opaque to x-rays is introduced into the blood stream of a patient through a catheter that has been placed in a given vessel. The vessel used depends on where the pathology is suspected to be. Once the catheter is in place the contrast material is injected into the patient's blood stream through the catheter while the patient is exposed to x-rays. The intensity of the x-rays passing through the patient's body are detected on film or detected electronically using a fluorescing screen that is backed by an image intensifier. The resulting image is a superposition of all the anatomical structures in the x-rays' path with the most dense structures appearing brighter than the less dense structures.
It is often necessary to observe many different angles in order to make a diagnosis with an angiographic system. It is known to rotate the x-ray tube and image intensifier in an arc around the patient taking many separate exposures and displaying the composite of all of the two dimensional images in a rotational way causing the resultant views to appear as three dimensional. However, because the image data is analog, the only rendering mode available is Maximum Intensity Projection (MIP). Further, each angle requires an injection of contrast material and a further exposure of radiation to the patient. As the number of radiation exposures increase, the radiation dosage to the patient problematically increases.
One solution has been to use an angiographic system in an angiographic room or suite for needle or catheter placement, and to use a computerized tomographic (CT) scanner located in another room or suite for performing diagnostic imaging while introducing contrast material into the blood stream of the patient. A problem with this solution is that the patient must be transported between separate diagnostic suites which takes time, and which could disturb any catheters and/or sensors which may be connected to the patient. Another problem is that maintaining two separate suites for housing two major pieces of diagnostic equipment is expensive.
Another solution has been to modify a CT patient table to allow a patient to be examined by a standard angiographic unit in one direction and by a CT scanner positioned 90.degree. relative to the angiographic unit within the same suite. An advantage is that the patient does not have to be transferred between suites. However, there are many redundant functions with this solution such as the filming device/imaging system and the display system that drive the cost of maintaining a single suite with a complete angiographic system and a complete CT scanner too high for practical use. Also, having to reposition (i.e. pivot) the patient support ninety degrees causes difficulties in some types of studies.
It is also known to use a portable or mobile C-arm fluoroscopic unit with a standard CT scanner in a CT suite to do biopsy needle guidance and very limited catheter placement work. However, this solution is limited by the inability of portable fluoroscopic units to achieve all the necessary positions for complex catheter placement procedures and insufficient power for x-ray generation.
Accordingly, it has been considered desirable to develop a new and improved angiographic system incorporating a computerized tomographic (CT) scanner which meets the above-stated needs and overcomes the foregoing difficulties and others while providing better and more advantageous results.